Rotating and movable bed gasifier producing high carbon char

ABSTRACT

The present invention includes a gasifier for gasifying fuels having a container with a top, sidewalls and a bottom for facilitating the gasifying process. One or more open vertical shafts extend downward inside the container for allowing a downdraft or updraft of air and fuel for the gasifying process. A rotating bed is preferably included inside the container and below the one or more shafts for receiving the fuel. The bed rotates essentially perpendicular to the shaft to facilitate even heating and gasifying of the fuel. The bed is further movable relative to the vertical shaft in order to increase or decrease the volume of fuel flow to the fuel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Application of U.S. Ser. No. 15/521,187, filedApr. 21, 2017, which is a National Stage of International ApplicationNo. PCT/US14/62024, filed Oct. 23, 2014, filed Feb. 11, 2013, all ofwhich are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to an apparatus for providing amore effective and efficient gasifier apparatus which produces a highcarbon ratio char product. More particularly, although not exclusively,the present invention relates to a rotating and movable bed gasifierapparatus.

Currently, there are many types of gasifier systems. Typically thegasification process is the primary energy generation means.Gasification generally takes materials, such as wood, coal, charcoal,agricultural residues, energy crops, municipal solid waste or otherbiomass materials, and gasifies them to make a “gas” used for power orelectricity generation or other uses, such as heat production. A typicalgasification system consists of a gasifier unit, a filtering system, andan energy converter.

Steam boiler/combustor units are also well-known, though their use forprimary energy generation has been questionable for some time, mainlybecause of the harmful resultant emissions. A steam boiler/combustorcreates high pressure steam used for power generation. Prior art systemsapply steam boiler/combustor units as secondary energy generation meansto gain energy and thus increase efficiency and reduce pollutants suchas gasses produced during the gasification process. An example of thistype of system can be found in U.S. Pat. No. 6,637,206 to Thiessen,which is herein incorporated by reference in its entirety.

One problem with fixed bed gasifiers is that there are inherent “hotspots” in the fuel, causing uneven gasifying. Some of these systems addmoving fingers to the fixed bed to agitate the fuel to aid in thegasification process. The torque force on the fingers increases as thediameter of the fire tube holding the fuel increases. This limits thesize of the gasifier which can be constructed. By creating too large agasifier, these fingers or the shaft holding them bend and break duringthe agitation.

U.S. Pat. No. 2,226,927 to Rundstrom is an up-draft gasifier which usesa grate system which reciprocates vertically, up and down, within afixed bed core to maintain an even flow of fuel and gas and allow forthe removal of ash. A problem with these vertically reciprocating bedsand fixed bed gasifiers is that the larger the gasifier, the more chancefor uneven heating inside the bed gasifier and thus poor gasifying ofthe fuel.

A further problem with immovable gasifiers is that as ash is built upduring the gasification process, fuel flow is reduced. This reduction infuel flow can result in decreased efficiency of the gasificationprocess.

A further problem with immovable gasifiers is that different fuelsrequire various amounts of fuel flow in order to maintain a proper andconsistent burn temperature. Without a proper volume of fuel flow to thefuel, the efficiency of the system is reduced.

Thus, in view of the foregoing, it is desirable to have an improvedgasifying system that solves these and other problems of the prior art.

Therefore, the primary feature or advantage of the present invention isan improved gasifier.

Another feature or advantage of the present invention is the provisionof a gasifier which reduces the size limitations in which a gasifierfuel mixer can be built.

Another feature or advantage of the present invention is the provisionof a gasifier that more uniformly heats the material being gasified toimprove efficiency.

Another feature or advantage of the present invention is the provisionof a gasifier that improves fuel flow to the fuel.

Another feature or advantage of the present invention is the provisionof a gasifier that preferably includes a rotating bed, is economical tomanufacture, durable in use and efficient in operation.

Another feature or advantage of the present invention is the provisionof a gasifier that preferably includes a movable bed for controlling thevolume of fuel flow to the burning fuel.

These and the other features or advantages of the present invention willbe apparent from the specification and claims that follow.

BRIEF SUMMARY OF THE INVENTION

One or more of the foregoing features or advantages may be achieved by agasifier having a container with a top, sidewalls, and a bottom forfacilitating the gasifying process. An open vertical shaft extends downfrom the top of the container and allows a downdraft or updraft of airto mix with fuel for the gasifying process. A rotating bed inside thecontainer preferably located below the shaft receives the fuel; the bedrotates essentially perpendicular to the shaft.

A further aspect of the present invention involves one or more fingersextending from a lower portion of the shaft for mixing the fuel with theair. The present invention may also include one or more fingers whichextend upward from the rotating bed for mixing the fuel with the air.The present invention also preferably includes a shaft attached to thebed for rotating the bed.

Another aspect of the present invention is an ash auger for removingused fuel from the container. Yet another aspect of the presentinvention is the provision of a gasifier which recycles the used fuelback into the shaft for reusing the fuel. Another provision of thepresent invention is a gasifier having a bed with sidewalls extendingupward to hold the fuel onto the bed.

Another aspect of the present invention is a gasifier having a bed whichmay be raised or lowered relative to the shaft so as to ensureconsistent and proper fuel flow to the burning fuel or char as ash isproduced.

One or more of the foregoing features or advantages may be achieved bythe gasifier having a container with a top, sidewalls, and a bottom forfacilitating the gasifying process, a first open vertical shaftextending inside the container, a second open vertical shaft inside thefirst vertical shaft creating a space between the first and secondshafts for allowing a downdraft of air and fuel for the gasifyingprocess in the space between the first and second shafts, and a rotatingbed inside the container, below the space between the first and secondshafts for receiving the fuel, the bed rotating essentiallyperpendicular to the shafts and moving essentially parallel to theshafts to control fuel flow into or from the fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a gasifier system assembly for using agasifier to create energy.

FIG. 2 shows a cut away view of one embodiment of a downdraft rotatingbed gasifier.

FIG. 2A shows the gasifier of FIG. 2 configured as an updraft gasifier.

FIG. 3 shows a top view of one embodiment of the vertical shaft shown inFIG. 2.

FIG. 4 shows a top view of one embodiment of the rotating trough or bedshown in FIG. 2.

FIG. 5 shows a cut away view of another embodiment of a rotating bedgasifier.

FIG. 6 shows a top view of one embodiment of the rotating bed shown inFIG. 5.

FIG. 7 shows a cut away side view of yet another embodiment of arotating bed gasifier.

FIG. 8 shows a top view of one embodiment of the rotating bed shown inFIG. 7.

FIG. 9 shows a cutaway view of still another embodiment of a rotatingbed gasifier.

FIG. 10 shows a cutaway view of still another embodiment of a rotatingbed gasifier with an adjustable fire tube.

FIG. 11 shows a view of the top of the gasifier taken along line 11-11.

FIG. 12 shows a cutaway of the side of the recess.

FIG. 13 shows a cutaway view of still another embodiment of a gasifierwith an adjustable height rotating bed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A. Introduction

The present invention relates to a rotating and movable bed gasifier.The present invention can be used in a system such as the system 10 asshown in FIG. 1. However, the present invention can be used in any typeof system where a gasifier for gasifying solid fuels is desired.

The present disclosure contemplates the use of a gasifier as a devicefor filtering dirty gas into one that is clean burning. Severalvariations of burning fuel and filtering are contemplated.

In a first example, a first combustion chamber is used to burn dirty (orsynthetic) fuel to produce dirty exhaust. The dirty exhaust is theninjected into the gasifier in combination with a fuel comprisingbiomass, such as treated seed corn or other well known biomass. The charresulting from the burning of the seed corn results in a filter which isutilized to purify the exhaust, thereby creating a clean burning usablegas. The clean burning usable gas is then transferred to a steam boileror like apparatus for converting heat energy into work or electricity.

In a second example, biofuel, such as treated seed corn or other wellknown biomass are combined with a dirty fuel prior to combustion. Theratio of dirty fuel to biofuel is preferably 20% to 80% (1:4), howeverother variations may also be used. The ratio of dirty fuel to biofuelmay depend on the particular dirty fuel used and the particular biofuel,as various dirty fuels produce a variable amount of pollutants andvarious biofuels have various filtering capabilities.

B. Rotating Bed Gasifier

Referring now to FIG. 2, a cut away side view of one embodiment of arotating bed gasifier assembly 20 is shown. The gasifier assembly 20begins with a gasifier container assembly 22. The gasifier containerassembly 22 generally has a cylindrical shaped sidewall 24. However, thesidewall 24 can be in any shape. Connected to the sidewall 24 is a top26 and a bottom 28. Preferably, the bottom 28 is an inverted cone-shapedpiece of metal to allow used ashes and overflow fuel or char to fall toa central point of an ash sump 30.

The ash sump 30 is connected to the bottom 28 of the gasifier containerassembly 22 preferably is connected to an ash auger 32 for removing thefuel and ashes after they have been through the gasification process andfallen to the bottom of the gasifier assembly 20. The present inventionmay use an elevator 33 which takes the char or fuel from the auger 32and recycles it back into the gasifier assembly 20. This allows for thefurther gasification of the char or fuel and creates a more efficientand more complete gasification of the fuel in the gasifier 20. Inaddition, less waste ashes have to be removed from the gasifier 20.Therefore, more complete gasification of the fuel is completed.

The waste ashes can be separated from the char or fuel by an ashseparator 35. The ash separator preferably has a screen 39 forseparating the waste ashes from the char or fuel which is to berecycled. Once separated, the ashes can be removed through the ashoutput 41 and the reusable char or fuel can be sent through the elevator33.

The char created in the process of the present invention generallycontains components that are of use in a variety of industries. Inembodiments of the invention, the amount of ash by total weight of thechar can be between 2 wt. % and about 20 wt. %, between about 4 wt. %and about 15 wt. %, or between about 7 wt. % and about 10 wt. %. Inembodiments of the invention, the amount of moisture by total weight ofthe char can be between 1 wt. % and about 15 wt. %, between about 2 wt.% and about 12 wt. %, or between about 4 wt. % and about 9 wt. %. Inembodiments of the invention, the amount of volatile matter by totalweight of the char can be between 2 wt. % and about 25 wt. %, betweenabout 4 wt. % and about 20 wt. %, or between about 7 wt. % and about 15wt. %.

The char itself is made of many components. The components of the charare ultimately determined by what biomass is used. Generally, the charwill have carbon and hydrogen. In embodiments of the invention, the charwill have a carbon content of at least about 50 wt. %, preferably atleast 55 wt. %, more preferably, at least 60 wt. %, most preferably atleast 65 wt. %. In preferred embodiments the char will include at leastcarbon, hydrogen, and nitrogen.

Thus, it has been found that the process of the present inventioncreates char which has a high carbon content, preferably a carboncontent of at least 50%. This means the char of the present invention'sprocess can be extracted and used in conjunction with other processes,such as using it with iron ore to make steel. The gas created by thegasification process in the gasifier assembly 20 can also be extractedfrom the gasifier 20 through one or more ports 34. The gas can then beused as an energy source for other systems.

Looking now at FIGS. 2 and 3, the gasifier assembly 20 has a verticalshaft 36 which extends through the gasifier container assembly 22creating a fire tube 37. Preferably, the shaft 36 has one or morefingers 38 extending from a lower portion of the shaft 36. The fingers38 can extend at any angle from the shaft 36. The fingers 38 allow forbreaking up the fuel as it falls down and enters the fire tube 37 andduring the gasifying process.

Below the shaft 36 is a rotating trough/bed 40. The rotating bed 40 isattached to a drive shaft 42 which is connected to a sprocket or pulley44 which is in turn connected to the motor 50 via another sprocket orpulley 52 and a chain or belt 54. There is preferably a bearing (notshown) at the top and the bottom of the drive shaft 42 to facilitateeven rotation of the drive shaft 42 and long life. There may also befingers 43 extending from the drive shaft 42 to aid in mixing the fuel.

The motor 50 is preferably geared down so the drive shaft 42 and therotating bed 40 rotate inside the gasifier assembly at approximately onerevolution every four minutes. This rotating or revolving bed 40 allowsfor the solid fuel which rests on the bed 40 and rotates with the bed 40to revolve, thereby creating more distribution of uniform heat withinthe circumference of the fire tube 37. This is accomplished by movingthe hot spots within the solid fuel around inside the fire tube 37thereby more uniformly heating the inside of the fire tube 37. Inaddition, the bed 40 can rotate intermittently and/or reversedirections.

Additionally, it is preferred, but not necessary, that the bed 40 havesidewalls 46 to reduce the amount of fuel falling off the bed 40 beforeit is thoroughly gasified. In other words, the fuel should remain on thebed 40 until the gasified fuel becomes high enough to fall over thesidewalls 46 and down to the ash sump 30. Furthermore, the bed 40preferably has one or more fingers 48 extending upward from the bed 40which allow the rotating bed 40 and the fuel to revolve and mix in acrossing path with the fingers 38 extending from the shaft 36. In otherwords, the fingers 38, 48 pass one another during revolution of the bed40 and mix the fuel. This aids in more thorough gasification of thefuel.

As shown in FIG. 4, preferably there are four spaced apart fingers 48 onthe bed 40. However, any number of fingers can be used. Preferably, thefingers 48 extend upward at any angle from the bed 40. In addition, thebed 40 can be made from solid sheet metal, perforated metal, expandedmetal, or any other material capable of holding the fuel which is to begasified. With or without holes the rotating bed 40, 78, 120, the ashbuilds up in the tray and falls over the side and into the gasifier'sbottom for removal.

FIG. 2A shows the gasifier assembly 20 configured as an updraft gasifierwith the air flow reversed. In this embodiment, the air can enter theport 34, pass through the fuel and exit as a gas upward through the firetube 37. Other aspects of the gasifier 20 remain the same.

FIGS. 5 and 6 show another embodiment of a gasifier assembly 60. Thisgasifier assembly 60 operates similar to the gasifier 20 shown in FIG.2. As shown in FIGS. 5 and 6, the gasifier 60 has a gasifier container62, with sidewalls 64, top 66 and bottom 68. Preferably, attached to thebottom 68 is an ash sump 70 and an auger 72 for removing the used ashes.In addition, an elevator or other device can be used for recycling theused ashes into the gasifier assembly 60. Again, the gasifier 60preferably has one or more ports 74 for allowing the gas created in thegasifier 60 to be directed out of the gasifier 60 and used.

In the embodiment shown in FIGS. 5 and 6, the gasifier 60 has a shaft 76extending downward or vertically into the gasifier container 62 creatinga fire tube 77. In the embodiment shown in FIGS. 5 and 6, the gasifierassembly 60 has a rotating trough or bed 78 connected to a drive shaft80 for revolving the rotating bed 78 similar to that shown in thegasifier assembly 20 of FIGS. 2 and 2A. Support brackets 81 support thebed 78 to the drive shaft 80. There is preferably a bearing (not shown)at the top and the bottom of the drive shaft 80 to facilitate evenrotation and long life. Preferably, the drive shaft 80 has a sprocket 82which connects to a motor assembly 50 for rotating the bed 78. Again, itis preferred that the bed 78 rotates approximately one revolution everyfour minutes, however other rotations can be used with the presentinvention. The rotating bed 78 has outside sidewalls 84 to help hold thefuel onto the bed 78. However, the rotating bed 78 has inside sidewalls86 which extend up into the shaft 76, thereby creating an elongatedring-shaped fire tube 77. This is best shown in FIG. 6. By beingconstructed in this manner, air can draft downward through the center ofthe inside sidewalls 86 and enter through optional vents 88 to providemore air for the gasification process. This type of rotating bed 78 alsohelps to reduce hot and cold spots within the gasifier assembly 60. Inaddition, the added air coming in through the vents 88 create improvedgasification of the fuel. In addition, this gasifier 60 can have updraftair flow.

Still another embodiment of the rotating gasifier assembly 100 is shownin FIGS. 7 and 8. Here again, the gasifier assembly 100 has a gasifiercontainer 102 with sidewalls 104, a top 106, bottom 108, ash sump 110,auger 112, and port 114. The gasifier assembly 100 shown in FIGS. 7 and8 has a first vertical shaft 116 and a second vertical shaft 118 locatedconcentrically inside the first vertical shaft 116. This creates anelongated ring fire tube 117 as shown in FIG. 8, that is similar to thatshown in FIG. 6. However, the second shaft 118 does not rotate with therotating trough/bed 120. Downdraft air can enter the second verticalshaft 118 and pass through optional vents 119 to enter the fire tube 117to aid in the gasification of the fuel. The rotating bed 120 is attachedto a drive shaft 122 by support brackets 123. There is preferably abearing (not shown) at both the top and the bottom of the drive shaft122 to facilitate even rotation and long life. A motor assembly 50 orother similar type driving device is used for creating the revolvingmotion of the rotating bed 120. It is preferred, that the rotating bed120 have outside walls 126 and inside walls 128 extending upward fromthe rotating bed to reduce overflow of the fuel until the gasifyingprocess takes its course.

It is understood that the rotating bed gasifier assemblies 20, 60, 100can have different shaped or designed rotating beds 40, 78, 120, 142. Inaddition, the rotating bed 40, 78, 120 can be created with sheet metal,perforated metal, expanded metal, or any other material suitable forholding the fuel which is to be gasified. Furthermore, the rotation ofthe bed 40, 78, 120, 142 can be any appropriate speed or direction. Itis preferred, however that the speed of the rotating bed 40, 78, 120 notbe so fast as to reduce or impede the gasifying process.

The preferred fuel for this gasifier is shelled corn. However otherfuels can be used. Air is sucked, blown, or both through the fuel whichis heated and pyrolyzed, forming gas for the gasification process. Thegasification process is self-sustaining with a blower (not shown)operating. The rotating bed 40, 78, 120, 142 replaces the function of afixed grate in standard gasifiers in the art. The gasification processgenerally continues until the blower (not shown) or rotating bed 40, 78,120 stops.

The direction of rotation of the rotating bed 40, 78, 120, 142 can beclockwise or counterclockwise. In addition, the bed 40, 78, 120, 142 canagitate or move intermittently, whatever motion works best for the fuelwhich is being used. It is preferred that the ring-type rotating troughs78, 120 are used in place of the pan-type rotating trough 40 once thespecifications require the rotating tray to be larger than approximately36 inches in diameter. This ensures better fuel agitation, which isnecessary to overcome the problems of biomass gasification. In addition,ring-type troughs also increases the rate of gasification bysubstantially increasing the reactive area in the gasifier 20, 60, 100.Rather than restricting the gas flow to the outside of the ring, aring-type trough may also allow gas to flow across the inside of thering, as best shown in FIG. 7. In addition to reinforcing the rigidityof the rotating tray 78, 120, the braces or brackets 81, 123 serve tomove char/ash to the removal sump 70, 110 where it can be augured out bythe auger 72, 112.

The recycling of char back into the fire tube 37, 77, and 117 uses anatural by-product of biomass gasification. Essentially, the char/ashauger 32, 72, 112 is elevated back to the top of the gasifier 20, 60,100 and reintroduced/recycled by combining it with new solid fuel orbiomass fuel which is being fed into the gasifier 20, 60, 100 for thefirst time. This greatly reduces the amount of ash produced in theprocess because it gets reused and further reduced each time it isreused.

In addition to biomass fuel, plastic fuel can be combined with biomassfuel to form a fuel blend. Because the plastic is a petrol-chemicalderivative, it burns much faster than the biomass fuel. As a result, afiltering effect with this blended fuel can be accomplished byintroducing dirty gasses from petrol/fossil fuels which are burnedseparately in a combustor similar to that as shown as a gasifier system10 in FIG. 1. Many dirty fuels cannot be blended in this way because ofmetal which is contained within them. Using dirty fuels with metalliccontents would clog the gasifier. Examples of such dirty fuels are tirefluff, medical waste, and circuit boards. However, if theplastics/rubber are homogeneous, blending them with biomass in theproper amount allows their clean burning while increasing the energyoutput from the gasifier. While any type of fuel can be used within thegasifiers of the present invention, it is noted that petro-chemicalderived fuels cannot easily be gasified by themselves. These fuels meltwhich in turn restricts the necessary air flow and therefore severelylimits or stops the gasification process.

It is widely known in the art that coal cannot generally be downdraftgasified easily. Therefore, a gasifier assembly 140 is shown in FIG. 9as an inverted downdraft gasifier. This gasifier assembly 140 workssimilar to the previously described gasifiers 20, 60, 100 with arotating bed assembly 142. This gasifier assembly 140 allows air to flowinward through one or more vents 144, through the fuel, and out throughone or more ports 148. This embodiment shows that either a top fuelinlet 150 or a bottom fuel inlet auger 152 can supply fuel into thegasifier 140. The top fuel inlet 150 allows for fuel to enter thegasifier assembly 140 and fall downward into the fire tube 154 forgasification. The bottom fuel inlet auger 152 similarly gets the fuel tothe inside of the fire tube 154, however, the bottom fuel inlet auger152 uses a mechanical auger for feeding the fuel into the fire tube 154.According to this embodiment, top fuel inlet 150 requires an airlock(not shown). It is preferred that the top input design would not be usedif rubber or plastic is mixed with the biomass fuel. In this case, it ispreferable that the bottom input design be used for the purpose ofcombining biomass fuel with petro-chemical derived fuels.

C. Movable Bed Gasifier

According to one embodiment of the invention, the bed 340 of thegasifier 220 is adjustable in height relative to either the fire tube337 or the enclosure 322, thereby regulating fuel flow to the burningfuel.

As previously described, as the fuel or char is consumed by the burningprocess, it produces ash. The bed 40 includes sidewalls 46 which reducethe amount of fuel falling off of the bed 40, thereby increasing theburn time of the fuel. As more fuel is added, however, fuel builds upinside the sidewalls 46 of the bed 40 and outside the shaft 36. Thisbuildup of fuel restricts the amount of air which may either enter (seeFIG. 2A) or exit (see FIG. 5) the shaft 37. This process also increasesthe amount of ash which is retained during the process, which increasesfiltration of the gas and insulation between the burning fuel and bed40. As a result, more complete combustion of the fuel may be realized byadjusting the gap formed between the sidewalls of the bed 40 and firetube 37. In most embodiments, the sidewalls are of a fixed height, andtherefore adjustment of the gap between the sidewalls and fire tubecorresponds to the gap between the fire tube and bed.

Several embodiments of the movable bed will now be described in detail.These embodiments are not intended to limit the scope of the inventionbut rather illustrate variations of the invention.

One specific embodiment is shown in FIG. 13. In this example, thegasifier 320 has an enclosure 322 with sides 324, top 326 and one ormore ports 334. Within the enclosure 322 is a fire tube 337 extendingdownwardly from the top 326 to a bed 340. The bed 340 has raisedsidewalls which serve to contain fuel, char and ash during thegasification process.

The bed 340 has a shaft 342 extending through. This shaft 342 is keyedto the bed 340 and a sprocket 344, thereby transferring rotationalmotion from the sprocket 344 to the bed 340. The sprocket is attachedvia a chain 354 to a motor 350 and sprocket 352 assembly. Below thesprocket 344 the shaft 342 has an external thread 360. This thread 360extends through a second motor 370. The second motor 370 includes, forexample, a worm gear which, when activated, adjusts the height of theshaft 342 and bed 340. It is also desirable in such a situation to havean adjustable motor mount 372 which may be engaged to adjust theposition of the motor 350 to maintain rotation of the bed 340.

According to an alternative embodiment, the enclosure 322 is separatedinto a top part 323 and an overlapping bottom part 325. Legs 358 supportthe bottom part 325 while a second support system (such as ascaffolding, legs, ceiling-mounted support, or other commonly knownstructure) supports the top part 323. The legs 358 are mounted to anelevator built into the floor 361. When it is desirable to adjust thefuel flow to the fuel by adjusting the gap between the fire tube 337 andbed 340, the elevator is raised or lowered. In this manner, fuel flowand burn rate are controlled without requiring sensitive components(such as an electric motor) to be exposed to falling ash and char.

According to an alternative embodiment, the bed 340 has a tube attachedto the bottom and surrounding the shaft 342. The tube is keyed to theshaft 342 along its length so the bed 340 may be adjusted up ordownwards as required without needing to adjust the shaft 342 and motor350. The tube may have a thread thereon, corresponding to a worm gear ona second motor 370.

According to an alternative embodiment, drive shaft 342 is a telescopingshaft, having one or more shafts located within the drive shaft 342. Theshaft forms the piston of a hydraulic or pneumatic piston. As hydraulicor pneumatic pressure is applied, the telescoping shaft extends, therebyraising the floor. The telescoping shaft may then be locked in thisposition by constant pressure or a mechanical interface, such as a pin,brace, screw, or other commonly known mechanical interface.

According to an alternative embodiment, bed 340 is attached to driveshaft 342 by a bearing and key, the key transferring rotation from thedrive shaft 342 to the bed 340, and the bearing allowing movement of thebed 340 up and down the shaft 342. A separate lift is attached to thebed 340, the lift providing vertical adjustment of the floor 40according to demand. This lift may be a single or series of hydraulicpistons, a worm gear and threaded rod, or other form of lift.

According to an alternative embodiment, the sidewalls of the bed areformed by a continuous tube extending from the floor 361 (or bottom ofthe enclosure) and overlapping the fire tube. The bed 340 is movable,according to any of the above discussed alternatives, so the height ofthe sidewalls and gap between the bed 340 and fire tube 337 is adjusted.

In operation, a fuel is selected from a group for which the optimal fuelflow is known. The optimal fuel flow for a given fuel may be determinedin a pre-production gasification process as the optimal rate of fuelflow may depend on the density of the fuel and consistency. The fuel isprovided to the bed where it is heated and the bed is rotated to provideeven heating throughout the fuel pile. As the fuel is combusted, ash isproduced, which builds up with the fuel or char on the bed against thesidewalls. Once the char and ash reach the height of the sidewalls, thematerial falls to the ash collector and the unburnt char is recycledinto the fuel source. As the ash builds up, the air passageway betweenthe bed and the shaft is occupied by the char and ash mixture.

At this point it becomes necessary for an operator to monitor thetemperature of the burning fuel or char and adjust the height of thefloor to increase or decrease fuel flow to the fuel or char. It isexpected that as ash and char builds up about the sidewalls of thefloor, the bed may be lowered to increase fuel flow to the burning fuelor char. As efficiency of the system is increased due to increased fuelflow, the ratio of ash to unburnt fuel is increased, which maynecessitate raising the bed to maintain fuel flow at a steady rate. Ittherefore may be necessary for an operator to continuously monitor thetemperature of the burning fuel or char, amount of ash production, andrate of fuel consumption in order to maximize energy captured during thegasification process.

It is also important to monitor the gas quality and quantity released bythe burning fuel or char. Gases such as CO (Carbon Monoxide), CO₂(Carbon Dioxide), H (Hydrogen), and oxygen are important gasses whichare used to determine both the quality of the useable gas but also theconsumption rate of the fuel. In the useable gas produced, high levelsof CO and H are desirable, while high levels of oxygen and CO₂ areundesirable as indicators of combustion. It is contemplated by thepresent disclosure that an automated monitoring system may determine theconcentration of these gases in the useable gas and adjust the height ofthe bed or fire tube as necessary.

As an alternative embodiment, pure oxygen rather than ambient air may beinjected into the system in order to produce a higher energy gas output.Other combinations of gasses may also be used without limitation, forexample, half ambient air and half pure oxygen. Further combinations areanticipated as being within the scope of this disclosure.

The term “fuel flow” as used incorporates several concepts. As fuel isconsumed and char and ash are produced, the lighter char and ash arepushed up the sidewalls of the bed. When this combination reaches theheight of the sidewalls, the ash and char are forced over the edge to becollected and/or recycled. Fuel consumption rate must therefore conformto the waste disposal rate. If more fuel is added, the consumption rateincreases and therefore the disposal rate must also increase. To do so,the bed may be adjusted so that more ash is disposed of from the bed.Additionally, the rate of consumption of the fuel is further limited dueto the insulative properties of the char.

D. Adjustable Fire Tube

A further embodiment of the present invention is illustrated in FIGS.11-13.

As in previous embodiments, the gasifier 220 includes a gasifiercontainer assembly 222 having side walls 224 a top 226, and furtherhaving a recess 228 adjacent the top 226. Within the gasifier containerassembly 222 resides the shaft 236 containing the fire tube 237. Beneaththe shaft is the rotating bed assembly 240 as previously described. Therotating bed assembly 240 is attached to a drive shaft 242 which is inturn connected to a sprocket 244 which receives power from a motor 250through a second sprocket 252 and chain 254.

The drive shaft 242 extends from a bearing (not shown) adjacent thesprocket 244 through the rotating bed assembly 240 and the fire tube237, terminating at the end of the fire tube 237 where it is supportedby a drive shaft sleeve 266. The drive shaft sleeve 266 itself isattached to a cap 262 on the top of the shaft 236 which forms the firetube 237.

FIG. 11 is a view taken along line 11-11, showing the top of the recess228. On the recess 228 are located three holes, a fuel opening 272 andan air opening 274. The air opening 274 is closable by an adjustablecover 276 which regulates the fuel flow through the fire tube 237. Thefuel opening 272 allows the fuel tube 238 (see FIG. 10) to pass through,delivering new or recycled fuel to the bed 240.

As shown in FIG. 12, three screws 264 pass through the recess 228 andengage the cap 262. The cap 262 has corresponding locations 268 (whichmay be weld nuts, tapped holes, threaded posts, or similar structureknown in the art) which receive the screws 264 (threaded rods,internally threaded bars, or other structure complementing the locations268). The screws 264 are not threaded completely into the locations 268,but rather a space is left between the cap 262 and the top of the recess228. By adjusting the screws 264, the cap can be raised or lowered asdesired. The cap 262 is permanently affixed to the top of the shaft 236,therefore as the cap 262 is raised or lowered by adjusting the screws264, the shaft 236 is raised or lowered relative to the rotating bed240.

As further shown in FIG. 10, the recess 228 is appropriately sized toaccommodate the fire tube 237 as it is raised or lowered. Additionally,the shaft sleeve 266 is sized appropriately so as to remain incontinuous contact with the drive shaft 242 which remains fixed as thecap 262 is raised and lowered.

While the current method of raising and lowering the fire tube 237 isdescribed as essentially a manual process, it may be preferable toautomate the process, thereby reducing risk to operators and allowingfor fully automated control of the gasification process.

As previously described in detail, it is necessary to maintain aconsistent fuel flow through the burning fuel in order to achieveoptimum combustion. By adjusting the height of the fire tube 237relative to the rotating bed 240, additional fuel flows to and throughthe burning fuel. By carefully monitoring the consumption rate of thefuel as well as the amount of unspent fuel discharged, the optimum gapsize can be determined.

Further, any of the above described methods for adjusting the height ofthe rotating bed relative to the fixed fire tube may also be adapted toadjust the height of the fire tube relative to a fixed bed. It may alsobe preferable in some environments to combine a movable bed with amovable fire tube. Such an arrangement is contemplated by the presentinvention.

While the present invention also applies to a rotating bed gasifier, itis not the intention of this disclosure to limit the adjustable bed andfire tube to a gasifier having a rotating bed. A fixed, nonrotating bedwould be just as well served by the contemplated improvement.

E. Conclusion

It is understood that even though specific references are made tocertain parts or sections of the invention in the figures, thesespecific parts or figures or design styles can be interchanged on any ofthe gasifiers as may be desired for a specific situation. In otherwords, any of the features or designs shown or contemplated can be usedon any of the contemplated gasifiers.

In the drawings and specification there has been set forth a preferredembodiment of the invention, and although specific terms are employed,these are used in a generic and descriptive sense only and not forpurposes of limitation. Changes in the form and the proportion of partsas well as in the substitution of equivalents are contemplated ascircumstance may suggest or render expedient without departing from thespirit or scope of the invention as further defined in the followingclaims.

EXAMPLE

An embodiment of the present invention is exemplified in the followingnon-limiting Example. It should be understood that this Example, whileindicating certain embodiments of the invention, is given by way ofillustration only. From the above discussion and this Example. Thus,various modifications of the embodiments of the invention, in additionto those shown and described herein, will be apparent to those skilledin the art from the foregoing description. Such modifications are alsointended to fall within the scope of the appended claims.

Char was created through the processes described in this application.The resultant char had a composition as shown the following tables.

TABLE 1 Replicate % Moisture % Volatile Matter % Ash 1 6.9655 10.16419.301 2 6.8877 15.508 8.877 3 5.9412 11.8407 8.088

TABLE 2 Weight Nitrogen Carbon Hydrogen Nitrogen Carbon Hydrogen Sample(mg) (%) (%) (%) (mg) (mg) (mg) 1 2.81 2.806 66.644 3.243 0.082 1.9400.101 2 2.25 2.839 66.539 3.391 0.066 1.551 0.084 3 2.45 2.819 66.6883.367 0.072 1.693 0.091

What is claimed is:
 1. A gasifier for gasifying fuels comprising: acontainer having an inside and an outside; a generally vertical openfire tube extending into the inside of the container and including oneor more fingers extending from a lower portion of the fire tube; arotating fuel bed located within the inside of the container and spacedfrom the one or more fingers of the fire tube wherein the distancebetween the bed and the fingers of the fire tube is greater than zero;an adjustable mechanism for elevating and lowering the fire tube, themechanism elevating or lowering the fire tube relative to the bed toadjust the distance between the one or more fingers of the fire tube andthe bed; and a motor and a drive shaft connecting the motor to the bedfor rotating the bed.
 2. The gasifier of claim 1 whereby the adjustablemechanism comprises a screw and threaded opening.
 3. The gasifier ofclaim 1 whereby the adjustable mechanism comprises a fluid pressureactivated piston.
 4. The gasifier of claim 1 whereby the adjustablemechanism is automated.
 5. The gasifier of claim 4 further comprising agas monitoring system for detecting levels of CO, H, and O.
 6. Thegasifier of claim 5 whereby the automated adjustable mechanism respondsto changes detected by the gas monitoring system.
 7. The gasifier ofclaim 6 wherein the bed has sidewalls extending upwardly.
 8. A gasifierfor gasifying fuels comprising: a container with a top, sidewalls, and abottom; a generally vertical fire tube extending downward from the topof the container to inside the container, the fire tube including one ormore shaft fingers extending downward from a lower portion of the firetube; a rotating fuel bed inside the container having sidewallsextending upwardly and spaced a distance below the fire tube; wherebythe bed is connected to a reversible motor, the reversible motorconnected to the bed to provide efficient heat distribution; and one ormore bed fingers extending upward from the bed for mixing the fuel;wherein the distance between the fire tube and the bed is adjustable. 9.The gasifier of claim 8 whereby the distance is adjustable by raising orlowering the bed and the bed and motor are movable together relative tothe fire tube.
 10. The gasifier of claim 8 whereby the distance isadjustable by raising or lowering the bed.
 11. The gasifier of claim 8whereby the distance is adjustable by raising or lowering the fire tube.12. The gasifier of claim 9 whereby the shaft is adjustable by means ofa screw and threaded opening.
 13. The gasifier of claim 9 whereby thefire tube is adjustable by means of a fluid pressure activated piston.14. The gasifier of claim 8 further comprising an ash sump and a devicefor recycling fuel back through the gasifier.
 15. The gasifier of claim14 wherein the device for recycling the fuel is an auger.
 16. A methodof gasifying biomass fuel comprising: selecting a fuel; inserting thefuel through a fire tube and onto a bed of a gasifier, the bed havingsidewalls extending therefrom; adjusting the gap formed between the firetube and sidewalls to provide fuel flow for optimal gasification basedon the fuel selected; supplying heat and air to the fuel; stirring thefuel to promote uniform gasification of the fuel; and adjusting the gapto provide consistent fuel flow as the fuel is gasified.
 17. The methodof claim 16 wherein the stirring of the fuel is by rotating a bed whichis supporting the fuel.
 18. The method of claim 17 wherein the bedrotation is about ¼ revolution per minute.
 19. The method of claim 16further comprising recycling fuel into the fire tube.
 20. The method ofclaim 16 wherein the gap is adjusted by raising or lowering the bed. 21.The method of claim 16 wherein the gap is adjusted by raising orlowering the fire tube.
 22. The method of claim 1 further comprisingforming char.
 23. The method of claim 22 wherein said char has a carboncontent of at least about 50 wt. %.
 24. The method of claim 22 whereinchar has a carbon content of at least about 60 wt %.
 25. The method ofclaim 22 wherein said char comprises carbon, hydrogen, and nitrogen. 26.A method of gasifying fuels comprising the steps of: providing agasifier having a fire tube and a bed with a sidewall extending upwardsabout the perimeter of the bed, the fire tube being positioned above thebed and vertically adjustable relative to the sidewall; providing a fuelconsisting essentially of 20% synthetic fuel and 80% biomass fuel;adjusting the height of the fire tube relative to the sidewall toachieve a preferred fuel consumption rate; delivering the fuel to thegasifier; and pyrolysing the fuel under conditions of high temperature,low pressure, and very low oxygen to produce a synthetic gas.
 27. Themethod of claim 26 further comprising forming char.
 28. The method ofclaim 26 wherein said char has a carbon content of at least about 50 wt.%.
 29. The method of claim 26 wherein char has a carbon content of atleast about 60 wt %.
 30. The method of claim 26 wherein said charcomprises carbon, hydrogen, and nitrogen.